Styrene-acrylonitrile (SAN) resins as copolymer resins prepared by polymerizing styrene (SM) and acrylonitrile (AN) have excellent transparency, chemical resistance, stiffness, and the like, and, thus, are broadly used in electrical, electronic, household, office, and vehicle components, and the like.
In addition, although SAN resins have excellent processability, impact resistance, and the like, they are applied to ABS resins having low heat resistance to reinforce heat resistance.
However, since the heat deflection temperature of SAN resins is approximately 100 to 105° C., application of SAN resins to products requiring high heat resistance is limited.
To provide high heat resistance, an α-methylstyrene (AMS) monomer is generally introduced into SAN resins. Since AMS has low depolymerization temperature and generates many oligomers with increasing polymerization temperature, heat resistance is decreased. Accordingly, unlike general SAN polymerization, AMS must be polymerized at low temperature and, as such, a polymerization rate is slowed.
To resolve such problems, although a method of extending reaction maintenance time, a method of adding a large amount of initiator, or the like is used, productivity is decreased, color of final products becomes poor, or poor molded products are produced due to molecular weight reduction.